Tub Lift My Hot Tub Cover Smells When I Lift It Off. It's A Newer Cover,so Is There Anything I Can Do Or Clean It With?

My hot tub cover smells when I lift it off. It's a newer cover,so is there anything I can do or clean it with? - tub lift

I am new to this and some spa pool, and I can any help or answers that I can get used to! Chemicals in water is very good, almost perfect, but just are not sure what to do with this cover too! Any help would be very grateful! Thanks